In the processing of integrated circuits, electrical contact must be made to isolated active device regions formed within a wafer substrate typically comprising monocrystalline silicon. The active device regions are connected electrically to conductive paths or lines which are fabricated above an insulator layer and which covers the substrate surface. To provide electrical connection between the conductive path and active-device regions, an opening in the insulator layer is provided to enable the conductive films to contact the desired regions. Such openings are typically referred to as "contact openings" or simply "contacts."
As the active area dimensions of a transistor approached one micron in diameter, conventional process parameters resulted in intolerable increased resistance between the active regions or areas and the conductive layer. To address this, a metal silicide is provided atop the active area prior to the application of the conductive film for formation of the conductive runner. Ultimately, an electrically conductive contact filling material, such as tungsten, would be provided for making electrical connection to the contact. However, tungsten adheres poorly to the silicide material which is normally employed. Additionally, it is desirable to prevent intermixing of the contact filling material with the silicide and the underlying silicon. Accordingly, an intervening layer is typically provided to prevent diffusion of the silicon, and the silicide with the plug filling metal and to effectively adhere the plug filling metal to the underlying substrate. Such material is accordingly also electrically conductive and commonly referred to as a "barrier layer" due to the anti-diffusion properties of same.
Following the deposit of the plug filling metal in the contacts, the integrated circuit will be subjected to other processing steps which may include severe temperature cycling and chemical mechanical polishing. These further steps may have a propensity, on occasion, to cause the electrically conductive plug to be displaced from the contact opening, thus electrically disconnecting the conductive plug from the underlying node.
It would be desirable, therefore, to improve upon the prior art integrated circuits, and methods for forming an integrated circuit for forming an electrical contact to an underlying silicon substrate.